This invention relates to die casting and clamp type machines and more particularly to the method and apparatus for adjusting tie bar tension or tonnage of the machine.
By use of the machine functions and individual tie bar drive motors each tie bar can be selectively or synchronously tightened either manually or automatically to compensate for uneven die expansion. The tie bar adjustment system is configured so that a tie bar can be removed from the system to enable a mold or die to be removed or inserted into the die casting machine.
In the die casting industry, the tie bar nuts hold the tie bars and the machine platens in rigid alignment when the die is closed and molten metal is shot into the die cavity. These bars are normally a simple threaded device with machined surfaces on the nut which abut the die casting machine platens. The machine's tie bars are under high tension (load tonnage) when closed during the shooting of metal into the die cavity to prevent flashing of the die. At this time these tie bars and nuts sustain the full impact of the shot in conjunction with the pre-load stress that is put on the bars of the machine when the machine is closed and locked up. Such bars must be adjustably tensioned to compensate for uneven die expansion at any one of the tie bar locations which are typically disposed with one bar in each quadrant of a die set-up. The clamp tonnage on a given machine tie rod determines the amount of compensation. The compensation must be maintained within limits to permit subsequent lock-up of the die halves. The system for tie bar compensation should enable the removal of these tie bars and nuts without a great deal of difficulty.
When a die is to be inserted or removed from a die casting machine or, for that matter, any type of clamp-operated machinery utilizing tie bars, it is sometimes necessary because of the size of the die itself to remove one or more of the tie bars so that the die can be removed from the machine.
In our invention, a separate drive motor is directly, continuously geared to the outside periphery of the tie bar nut. Each drive motor can be driven separately to cause the tie bar nut to be rotated to individually adjust tension in a selected tie bar. Means are provided to synchronously drive all tie bars to assure compensation of uneven die compensation while maintaining machine lock-up capabilities.